Over the moon Informal

Extremely happy, delighted, or thrilled about something.

It’s a warm, informal way to express joy, often used about good news — a new job, an engagement, a birth — rather than everyday small pleasures.

The phrase is generally traced to the English nursery rhyme “Hey Diddle Diddle,” whose best-known line describes a cow jumping over the moon; the rhyme was first printed in roughly its current form around 1765 in “Mother Goose’s Melody,” though scholars have found possible hints of it existing earlier, including a 1569 play by Thomas Preston that mentions “hey-diddle-diddle” as the name of a dance, suggesting the rhyme (or at least its refrain) may already have been familiar by the sixteenth century. Most of the more elaborate theories linking the rhyme to specific historical events or figures are considered discredited by folklorists, who treat it primarily as nonsense verse rather than coded history. How exactly the absurd image of a cow leaping over the moon came to represent being “delighted” isn’t precisely dated, but reference sources do confirm the nursery rhyme as the acknowledged source of the idiom; its use as an everyday expression of joy became especially widespread in twentieth-century British English, closely associated with post-match football interviews in which delighted managers and players were, and still are, famously “over the moon.”

She was over the moon when she found out she got the scholarship.

We were over the moon about the new baby’s arrival.

He’s been over the moon ever since the promotion came through.

A: How did she react to the proposal? B: She was completely over the moon.